Optimization of Ski Jumper’s Posture Considering Lift-to-Drag Ratio and Aerodynamic Stability in Pitch

Abstract

In the present study, an optimization of ski jumper’s posture using a surrogate model has been numerically performed to improve lift-to-drag ratio and to examine aerodynamic stability in pitch to ensure flight control and safety. Three-dimensional Reynolds-averaged Navier-Stokes equations are discretized by finite volume approximations for the flow analysis, and the shear stress transport turbulence model is used as the turbulence closure. Airfoil theory and principles of aircraft stability are used to examine the stability mechanism. To enhance aerodynamic stability in ski jumping, the ranges of design variables are determined to have a static margin value within 5∼25%. Two angles of ski jumper’s posture are chosen as design variables through a preliminary test and the lift-to-drag ratio is used as an objective function for the present optimization problem. Twelve design points within design spaces are selected by Latin hypercube sampling. To approximate the objective function in the design space, the Kriging model is constructed using the numerical results on the design points, and the optimal point is found by sequential quadratic programming. The predicted values of the design variables and the objective function for the optimal and the reference design, as well as corresponding results of numerical calculation. The Kriging model predicts the objective function values at the optimum points with only 1.61% error in comparison with the values obtained the RANS analysis. And, the optimum design shows not only improved lift-to-drag ratio but also increased longitudinal stability in ski jumping as compared to the reference design.